Programmable materials

ABSTRACT

Programmable material is a collection of substantially cubic shaped bricks called monomers that move relative to each other under computer control to sculpt engineering structures ( 5 ) and mechanisms ( 6 ) (walking machine) illustrated in the figure. The monomers have features to lock to other monomers and slide relative to other monomers without separating. The monomers are fault tolerant against damage; functional monomers move faulty monomers and replace them with functioning clones. Movement of monomers is broken down systematically into streamers, gateways, highways and reservoir methods to obtain individual monomer movement paths required to synthesise a structure. Specialised monomers can carry tools which together with synthesis of custom structures create custom machines.

[0001] The present invention relates to a programmable material.

[0002] Traditionally, machines and engineering structures have beenconstructed from parts each designed to perform a specific function at aspecific position in a machine or structure. Such an approach limits theusefulness of the parts in other machines or structures.

[0003] The present invention reflects a very different approach to thedesign and construction of machines and structures.

[0004] The invention provides a machine of substantially parallelepipedshape, having means for so interacting with identical machines as tocause relative transport of them and the machine, and means forinteracting with identical machines so as to secure the machine inposition relative to them.

[0005] The machine is of substantially parallelepiped shape so thatrows, sheets and blocks of closely spaced, or adjacent identicalmachines can be formed. They are also of that shape so that a machinemay move or be moved over such a row or sheet whilst keeping one of itsfaces parallel and close to or adjacent to the exposed faces of themachine of the row or sheet. Clearly the machine may depart from anexactly parallelepiped shape by the removal of parts of its faces notneeded for interacting with neighbouring machines.

[0006] The machine may be responsive to external signals communicated toit so as to effect the transport and securing.

[0007] Additionally or alternatively, the machine may incorporate acomputer and be responsive to signals generated by that computer so asto effect the transport and securing.

[0008] The securing means or the transporting means or both may compriseelectromagnets.

[0009] The transporting means or securing means or both may comprisemechanical parts or features on the machine that interlock withcomplementary parts or features on identical machines.

[0010] The transporting means may comprise mechanical parts or featureson the machine that can be caused to interlock with complementary partsor features on an identical machine in such a manner as to allowrelative motion of the machines along particular axes. Those parts orfeatures may be arranged to provide two or more independently engageableinterlocks between the machine and an identical machine, each of whichallows relative motion of the two machines only along a respective oneof two or more different axes.

[0011] The interlocking parts or features may comprise a memberextensible from the machine into a recess or groove in an identicalmachine, the member incorporating extensible wedges for locking themember in the recess or groove.

[0012] The interlocking parts or features may comprise pairs of members,the members of a pair being extensible from a face of the machine, indifferent directions at an angle to the normal to that face, intorespective ones of a pair of recesses or grooves in a face of anidentical machine.

[0013] The interlocking parts or features may comprise pairs of members,each member of a pair being mounted to pivot between a withdrawnposition and an extended position. Advantageously, the members of a pairreceive at their withdrawn positions, in respective grooves in themembers, respective ones of a pair of opposing lips from an identicalmachine.

[0014] The machine may comprise a plurality of studs on a face of themachine engageable with a neighbouring identical machine so as to locateit in position, the studs being retractable so as to release theneighbouring machine.

[0015] The studs may be engageable with interlocking mechanical parts orfeatures of the neighbouring machine.

[0016] The studs may be depressible by an identical machine that isadvancing to become such a neighbouring machine.

[0017] The machine may be of substantially cuboid shape, which ispreferably a cube.

[0018] The machine may have four means on each face of the machine forcommunicating power or data with neighbouring identical machines, thosemeans being located in the same positions on each face and being solocated either on each of the diagonal centre lines or on each of theorthogonal centre lines of each face as to preserve the four-foldrotational symmetry of the face.

[0019] Additionally or alternatively, the machine may have coaxiallyarranged means mounted centrally on each face for communicating power ordata with identical machines as to preserve the four fold rotationalsymmetry of the face.

[0020] Additionally or alternatively, the machine may have four pairs ofan input means and an output means for communicating data withneighbouring identical machines, those means being located in the samepositions on each face and the input means and output means of each pairbeing so located symmetrically to either side of each of centre lines ofthe face so as to preserve the four-fold rotational symmetry of theface.

[0021] The invention provides a machine equivalent in size to aparallelepiped block of a plurality of machines according to theinvention, that is not composed of such machines and that has means forso interacting with such machines as to cause the relative transport andsecuring that would occur if the machine consisted of a parallelepipedblock of machines.

[0022] The invention further provides structures and machines assembledfrom machines according to the invention.

[0023] The invention also provides a method of moving a first machinefrom a first site aligned with and neighbouring a second site, in adirection parallel to the neighbouring sites, wherein each site is amachine according to the invention.

[0024] The first machine may have neighbours that are secured to it andthat move with it.

[0025] The method may be repeatedly applied to move a machine along arow of machines, and advantageously that motion is continuous.

[0026] The invention further provides a method of extending by one unit,a streamer of units in a row ending in a tip unit, the units eitherbeing single machines according to the invention, or beingparallelepiped blocks of such machines, the method comprising moving apair of units along the streamer until one of the pair is a neighbour ofthe tip unit and the other extends beyond the tip unit, and moving theother unit of the pair from being a neighbour of the one unit to being aneighbour of the tip unit, in which position it becomes the new tipunit, the movement of the machines being according to the invention.

[0027] The invention also provides a method of extending by one unit astreamer of units in a row beginning in a base unit, the units eitherbeing single machines according to the invention, or beingparallelepiped blocks of such machines, the base unit having one or moreneighbouring machines that are not in the row, the method comprisingadding an extra unit to the row before the base unit and advancing therow relative to the one or more machines neighbouring the base unit adistance of one unit in the direction that results the extra unit movingto the original site of the base unit.

[0028] The invention also provides a method of retracting a streamercomprising reversing the steps of either of the methods of extending astreamer according to the invention.

[0029] The invention further provides a method of delivering machinesaccording to the invention from a first point to a second point,comprising constructing from such machines a structure connecting thetwo points and moving the machines along the structure from the firstpoint to the second point.

[0030] The invention also provides a method of constructing a structurecomprising machines according to the invention, the method comprisingeither of the methods of extending a streamer according to theinvention.

[0031] By analogy with plastics chemistry, the individual machines willbe referred to as “monomers” in the description, which follows, ofexamples of the present invention. Clearly the correspondence is notcomplete; for example, chemical monomers do not transport each other.

[0032] The ability of the monomers to transport each other means thatthe material can form itself into structures without the need for toolsto fashion it. To build a structure, monomers are delivered by thematerial itself to desired positions. The material is programmable inthe sense that many different structures can be built from the samemonomers and so a “programmable material” is a name which can be givento a collection of monomers.

[0033] There will now be described, by way of example only, materialsaccording to the present invention and methods according to the presentinvention of forming them into structures and machines. Reference willbe made to the accompanying Figures, of which;

[0034]FIG. 1 shows some basic structures formed from cubic brickmonomers.

[0035]FIG. 2 shows some further structures formed from the monomers.

[0036]FIG. 3 shows normal and L-type streamers.

[0037]FIG. 4 shows a monomer which has grooves along the orthogonalcentre lines of each face.

[0038]FIGS. 5a and 5 b show the monomer with locks being extended andwith the locks in the fully extended position respectively.

[0039]FIG. 6 shows the mechanism for extending the locks.

[0040]FIG. 7 shows wedges extensible from the locks.

[0041]FIG. 8 shows the mechanism for extending the wedges.

[0042]FIGS. 9a-d show some cross sections of two neighbouring locks ofthe monomers and how they interlock.

[0043]FIG. 10 shows how the monomers are made to move relative to eachother.

[0044]FIGS. 11a and 11 b show the positions of the gears used to movethe monomers.

[0045]FIGS. 12 and 13 show the mechanism for driving the gears.

[0046]FIGS. 14a-c and 15 a-g show the locks in various positions fortransporting and securing monomers.

[0047]FIGS. 16a and 16 b shows a mechanism for locating the monomers inposition.

[0048]FIGS. 17a-d show a second type of monomer and its mechanisms fortransporting and securing identical monomers.

[0049]FIGS. 18a and 18 b show configurations of wedges of the secondtype of monomer for transporting and securing of other identicalmonomers.

[0050]FIG. 19 shows a partly complete monomer of a third type.

[0051]FIG. 20 shows the operation of the hinged locks used in the thirdtype of monomer for transporting and securing.

[0052]FIGS. 21 and 22 show a variant of the hinged locks.

[0053]FIG. 23 shows a wall of electromagnetic monomers.

[0054]FIG. 24 shows connections between the faces of a monomer for dataand power.

[0055]FIG. 25 shows an arrangement for the contacts for data and poweron the surface of a monomer.

[0056]FIGS. 26a-e show how an L-type streamer grows.

[0057]FIGS. 27a-e show the growth of an L-type streamer where the unitsare 2×2×2 blocks of individual monomers.

[0058]FIGS. 28a-d show the growth of an L-type streamer where some ofthe units are 2×2×2 blocks of individual monomers and some are largermonomers of an equivalent size.

[0059]FIGS. 29a-f show methods for changing the direction of growth ofan L-type streamer through 90°.

[0060]FIGS. 30a-i show a method of turning a streamer comprised of 2×2×2units through 90°.

[0061]FIG. 31 shows a tower formed of monomers.

[0062] Referring to the accompanying drawings, and initially to FIG. 1,monomers 1 are in the form of cubic bricks. Each monomer is provided oneach face with means (not shown in FIG. 1) for securing it face-to-facewith another similar monomer and for causing relative movement of thetwo monomers parallel to the edges of the face. The monomers can beassembled to form almost any desired shape, and as examples a solidblock 2, a wall 3, and a flat sheet 4 are shown in FIG. 1. A solid blockcan be thought of as being composed of a series of adjacent solid wallsor as flat sheets stacked together. FIG. 2 shows some further shapes 5and 6. The shape 5 is yet another object that is contained within thesolid block 2 depicted in FIG. 1. Just like the walls and sheets, thereare many other objects that can be contained in a solid which can berealised if an existing set of monomers is sculpted or re-arranged byaddition of monomers, removal of monomers, re-arrangement of monomers,or a combination thereof. This kind of sculpting or re-arrangement canbe achieved by using the means incorporated in the monomers to movemonomers around the surface of the object, as is described in moredetail below. Computers and software can be used to control the movementof the bricks to automate the shaping process.

[0063] The bricks can be arranged into machines, for example, a walkingmachine 6 as is shown in FIG. 2. It is shown below how to make themachine 6 walk.

[0064] There are important mechanisms, which will be described in depthbelow, that are the building blocks of basic programmable materialoperation. As a brief example of these, two such mechanisms are shown inFIG. 3, the normal streamer 7 and L-type streamer 8.

[0065] The normal streamer 7 is a rod-like protrusion which can grow outof a surface. The rod grows in a direction normal to the surface. It isextended one monomer at a time by attaching a monomer at the rear of therod and pushing the rod out. The L-type streamer 8, on the other hand,grows by attaching more monomers one at a time to the front of thestreamer. These mechanisms are fully reversible. That is, they cancontract as well as grow.

[0066] Having briefly discussed structures formed from monomers, themonomers themselves will now be examined in more detail.

[0067] Referring to FIG. 4, one form of monomer indicated generally bythe reference numeral 1 is cubic in shape and has a pair of grooves 11in the shape of a cross on each face, dividing the face into four. Thegrooves 11 are called major grooves. The walls of the grooves 11 eachhave an additional groove 12 etched into or otherwise formed in them andthis is called the minor groove. This minor groove will provide thenecessary grip when monomers are sliding along the underside of othermonomers or when scaling walls.

[0068] The major groove 11 contains within it locking and tractionmechanisms (not shown in FIG. 4). The locking mechanism allows formonomers to be firmly locked together. The traction mechanism allows themonomers 1 to move relative to each other. When moving, the monomers 1must not separate since they could be travelling along the underside ofother monomers 1 or they could be scaling walls.

[0069] Referring to FIG. 5, both the traction and locking mechanisms areprovided, at least in part, by retractable flange-like protrusions onlocks 13, located within the major grooves 11 of each monomer 1, whichcan be extended and can reach into the major groove 11 of an adjacentmonomer 1. On each face of the monomer 1 there are four of these locks13, one in each arm of the cross formed by the major grooves 11. Thelocks 13 are operated as two pairs, each comprising of the two alignedlocks in a single major groove 11. If one pair of locks is extended,then the two adjacent monomers can slide relative to one another only inthe direction of the major groove in which those locks are. If bothpairs of locks are extended, then the two monomers cannot slide past oneanother in any direction.

[0070]FIG. 6 shows how the lock 13 is pushed out of and is retractedinto its monomer 1. A motor 21 fixed within the monomer 1 below themajor groove 11 has a screw spindle 22 that extends or retracts as itrotates, depending on the direction in which the electric motor rotatesit. The end of the spindle 22 is connected to the lock 13 by aball-and-socket decoupling mechanism 40 in such a manner that as thespindle screws in or out, the lock is extended or retracted withoutrotating.

[0071] The locks 13 have retractable wedges 14 (see FIG. 7) inside them.These wedges 14 have to be fully retracted into the lock 13 when thelock is being retracted into or extended from its major groove 11, butonce it has reached into the major groove 11 of another monomer 1, thewedges 14 are pushed out and engage in the minor grooves 12 of theadjacent monomer. The wedges 14 then lock the two monomers 1 togethersuch that they can slide along the axis of the pair of locks but cannotseparate. The wedges 14 have toothed edges 19 for a rack and pinionmechanism which will be employed to move the monomers 1. Also shown inFIG. 7 are power and signal contacts 15 which are on the surface of thelocks 13. When the locks 13 are inserted into the major groove 11 ofanother 1 for locking, the contacts 15 make electrical contact with thecorresponding contacts on the locks 13 belonging to the other monomer,which are in their retracted position at the bottom of the major groove11 of that other monomer. The contacts are pads of a conductor materialdeposited on a insulating material which is deposited on the metal ofthe lock. The low profile of these pads allow the locks to slide pasteach other when neighbouring monomers are moved. An alternative is tohave a plug and socket arrangement in which the plugs of one lock can beextended to engage with the sockets of the lock of a neighbouringmonomer. Such plugs would have to be retracted before monomers aremoved.

[0072]FIG. 8 shows the mechanism used to push and pull the wedges 14 inand out. A rotary cam 16 has an oval groove 18 in which engages pins 17to which the wedges 14 are attached, so that as the cam 16 rotates thepins 17, and with them the wedges 14, are moved symmetrically in andout. The rotation of the cam 16 is under the control of an electricmotor 20 which is geared down to provide a sufficiently high drivingforce and slow speed of operation.

[0073]FIGS. 9a to 9 d show the operation of the locks 13 with the wedges14. The cut-away section of the two monomers 1 in FIG. 9a shows thelocks 13 of both monomers fully retracted. In FIG. 9b, the lock 13 fromthe top monomer 1 has extended down into the monomer 1 below. Thecontacts 15 are not shown in FIG. 9, but at this point they are engaged,enabling power and signals to be transferred from one monomer to theother. In FIG. 9c the wedges 14 are extended and the monomers locktogether. The monomers 1 are now inseparable, but because the lock 13and its wedges 14 confine the monomer in only two axes (movement notpossible left to right or up and down as seen in FIG. 9c), the monomers1 are free to slide relative to one another in and out of the plane ofthe paper. This mechanism is reversible and can operate as shown in FIG.9d, where the monomer 1 at the bottom has locked to the top monomer 1.

[0074] It will now be described how, following on from FIG. 9c, the topmonomer 1 can be moved. FIG. 10 shows two monomers locked together by alock 13 extended from the top monomer 1 to the bottom monomer 1. Thetoothed racks 19 on the wedges 14 of the lock 13 engage pinion gears 23of the bottom monomer. That provides a rack and pinion mechanism bywhich the monomers can be moved relative to each other. A pair of gears23 opposite one another on either side of a major groove 11 are linkedby large gears wheels 25 below the major groove. As shown in FIG. 10,the pair of gears 23 is driven by an electric motor 24 on the spindle ofone of the gears.

[0075] The number of gears 23 and their locations on a typical face of amonomer 1 are shown in FIGS. 11a and 11 b. The use of several pairs ofgears 23 along a major groove 11 is required to ensure that, as a topmonomer 1 is moved along a row of bottom monomers 1, when the leadinglock 13 of a pair is pushed along on to the next monomer 1 in the row,the wedges 14 of the trailing lock 13 of the pair are still engaged bygears 23 until the first pair of gears 23 of the next bottom monomer 1grips the wedges 14 and starts to pull the top monomer.

[0076] All of the gears 23 on one face of a monomer 1 can turn at thesame time, with a consequent simplification of the control and drivetrains. This is because, at any time, when movement is to occur, onlyone pair of locks 13 are engaged, either as shown in FIG. 11a or asshown in FIG. 11b, and the gears 23 in the other major groove 11 canrevolve freely.

[0077] A top view of the gears 23 and their linking gear wheels 25 (inoutline) are shown in FIG. 12. Wherever there is overlap between thelinking gear wheels 25 as seen in plan view, they are placed atdifferent heights to avoid any spatial conflict.

[0078] As shown in FIG. 13, a system of toothed belts 26 connects thegears 23, transmitting the drive from one pair of gears 23 to another.Only one motor 24 is then necessary for all of the gears 23 along amajor groove 11, and it is ensured that all of the gears will rotate atthe same speed. The belts 26 are held against the gears 23 by a set offree spinning rollers 31 (also shown in FIG. 13). Two belts 26 areneeded to drive all the gears 23 of one face of the monomer, one beltfor each of the two axis. The two belts 26 are set at different heightsso that they do not interfere with each other. These belts 26 are setbelow the locking mechanism so that they do not interfere with the upand down motion of the locks 13. One large gear wheel 27, which may beone of the large gear wheels 25, on each belt 26 is meshed with asimilar large gear wheel 27 on the other belt 26, as shown dotted inFIG. 12. That links all the wheels together so that one motor 24 candrive them all.

[0079] As shown in FIGS. 9c and 9 d, there is a gap maintained betweenthe monomers 1 as a result of the engaged wedges 14. This gap can bevery small (less than 100 micrometers) or it can be set to around 1-2millimetres. To make sure that the monomers 1 are not touching at anytime, the gap needs to be wide and set around 1 millimetre. Too small agap means that the mechanism could jam. This is important as monomers 1are continually being moved relative to one another in use, and theyshould not rub against each other. Mechanisms such as the normalstreamer 7 (FIG. 3) are particularly prone to jamming without goodinter-monomer gap. The clear gap can be seen in FIGS. 1 to 4 where themonomers are drawn as separate bricks. Preferably the gaps are set suchthat the monomers 1, apart from their locks 13, never touch.

[0080] With monomers 1 that do not touch, stability of a structure ismaintained by ensuring that the locks 13 are made of strong materials.Additional bolts can be employed on the surface of the monomers 1 toprovide even more rigidity when in a locked position.

[0081] When moving monomers 1, the locks have to provide for stabilityand tolerate vibration. Stability can be provided by wider lockmechanisms that stop rocking movement. The width of the lock determineshow stable a monomer is as it is moved. Thinner locks will tend topermit the monomers to wobble more as they are moved. Wider locks areless economical. A width of around one quarter to one fifth of the totalwidth of the monomer is believed to be in general a reasonablecompromise where mechanical stability is ensured for economic use ofmaterials.

[0082] To allow the monomers to move, there must be some play when onepair of locks 13 are engaged. However, when both pairs of locks 13 areengaged so as to secure the monomers 1 in position, this play is notdesirable. This problem can be avoided by engaging the wedges 14 furtherso that they engage into the other monomer 1 more tightly. The wedges 14thus have three operating positions—fully withdrawn, partially extended(when relative motion of the monomers is desired) and fully extended(when it is desired to secure the monomers).

[0083] Before a monomer 1 is moved, there are a variety of startingpositions for the locks 13. The monomer that is to be moved may have allits locks 13 extended into the body of another monomer 1. The othermonomer 1 may have its locks 13 extended into the monomer 1 that is tobe moved. Another situation is that locks 13 extend from both monomers 1into each other. These starting positions may have to be changed tocorrect the insertion of the locks 13 before the monomers 1 are moved inthe desired direction.

[0084] Consider FIGS. 14a-c and 15 a-g which show the locks 13 indiagrammatic manner in cross section of a monomer 1. Not all locks canbe represented because the monomer is three dimensional, but the twodimensional section is sufficient to illustrate many points regardingmovement of monomers. In each of FIGS. 14a to 15 g, for each of the foursectioned faces of the monomer there are shown in side view the twolocks 13 in the major groove 11 that runs along the plane of the paperand, between them, an end view of one of the locks 13 in the majorgroove 11 perpendicular to the plane of the paper.

[0085]FIG. 14a shows all the locks 13 retracted. FIGS. 14b, 14 c, 15 aand 15 b show a series of examples where various groups of locks havebeen pushed out, as if to engage neighbouring monomers (not shown).

[0086]FIGS. 14c and 15 a show left and right pairs of locks in the planeof the paper extended. In FIG. 15a, that allows the monomers to move upor down, propelled by the gears 23 in the monomers to its left, while inFIG. 14f the right monomer 1 has pushed into the left monomer 1 the pairof its own locks 13 that is at right angles to the locks 13 extendedfrom the left monomer 1, so that the two monomers are locked togetheragainst movement in any direction.

[0087]FIGS. 14c and 15 b show locks 13 normal to the plane of the paperextended. In FIG. 15b that allows the monomer to move into or out of theplane of the paper, propelled by monomers to the left, while in FIG.14f, as noted above, the two monomers are locked together.

[0088]FIG. 14b shows all of the locks 13 on one face of a monomer 13extended, fixing the monomer relative to that adjacent to it.

[0089]FIGS. 14b and 14 c illustrate two locking schemes where pairs ofmonomers 1 are locked to each other. The locking method of FIG. 14b fromhere on will be known as the “face lock” while the method of FIG. 14cwill be known as the “complementary lock”. The face lock is more suitedto pick up dead or passive monomers 1 that have major grooves 11 andminor grooves 12 (but do not have locks), such as tools and equipmentintended for use in conjunction with the monomers. A dead monomer 1 is amonomer 1 which is faulty and is unable to operate its locks 13 oncommand. Another use of the face lock is to latch onto structuralsupports (which are normally not active) for grip while climbing andmoving about. The complementary lock on the other hand provides betterstructural strength because of the way stresses are evenly distributedbetween two monomers 1, and is therefore usually preferred for lockingtogether two active monomers.

[0090] It has been mentioned above that engaging only one pair of locksallows the monomers 1 to slide along the axis of that pair of locks.FIGS. 15a and 15 b show two possibilities, “sliding configurations”, ofthe locks 13 engaging to allow movement of a monomer 1 across a face ofa monomer 1. These movements are at right angles to each other.

[0091] In FIG. 15a the monomer on the right has its lock inserted intothe monomer 1 on the left. The left monomer 1 activates its motors tomove the right monomer up and down. Notice that while the right monomeris moving, it does not need power. The power to that monomer is switchedoff. It is effectively dead and all control over it, including itsmechanisms, and its status, are lost. The mechanical power needed tomove the monomer 1 is provided by the stationary monomers 1 on the leftwhich use their electric motors 24. When the monomer 1 that is beingmoved reaches its destination, power can be routed into it once againthrough the locks 13 to regain control of its internal mechanisms.

[0092] In FIG. 15b the monomer on the right has its locks extended intothe monomer on the left and can be moved into and out of the plane ofthe paper by a motor 24 of the left monomer 1.

[0093] There are several initial starting positions from which the locks13 must change configuration to end up in one of the slidingconfigurations shown in FIG. 15a or in FIG. 15b. FIG. 15c shows atypical 3×3 array of monomers with a large variety of startingpositions.

[0094]FIGS. 15d and 15 e show how to get from two different possiblecases of face lock to a sliding configuration. FIGS. 15f and 15 g showhow to get from two different possible cases of complementary lock tothe sliding configuration. These four cases cover all the possiblecombinations of a starting position. It should be noted that in allinstances, while the locks 13 are changing configuration, powertransmission and mechanical locking between the monomers 1 are alwaysmaintained through at least one set of locks 13. Only one set of locks13 is retracted or inserted at any one time. Also, the clear separationgap between the monomers 1 is always maintained during the operationbecause the wedges 14 of one set of locks 13 are kept extended when thelocks of the other set are being moved.

[0095] The wedges 14 of the locks 13 that are being moved are retracted.If the wedges 14 are not retracted, then the locks 13 cannot be movedunless all of them are moved simultaneously. If they were all moved, theeffect would be to change the inter-monomer gap, which in general shouldnot be allowed to happen. The computer or other controller shouldtherefore ensure that the wedges 14 on any lock 13 are retracted beforethat lock is moved. There are, however, instances when moving the locks13 with the wedges 14 engaged makes sense. For example, in the erectionof semi-permanent structures, the monomers may be “parked” by reducingthe inter-monomer gap to zero to clamp them together as rigidly aspossible.

[0096]FIG. 15d shows one case of a face lock in which all four of thelocks of the right monomer 1 are extended into the left monomer 1. Tofree the right monomer 1 for movement by the motor 24 of the leftmonomer 1, one pair of the locks 13 of the right monomer 1 is simplyretracted.

[0097]FIG. 15e shows the other case of a face lock, in which all four ofthe locks 13 of the left monomer 1 extended into the right monomer 1. Tofree the right monomer 1 for movement the face lock is first convertedinto a complementary lock by withdrawing the pair of locks of the leftmonomer 1 that lies along the direction of intended movement andextending the corresponding pair of locks 13 of the right monomer 1.Then the remaining extended pair of locks of the left monomer 1 iswithdrawn.

[0098]FIG. 15f shows the case of a complementary lock in which it isonly necessary to withdraw the extended pair of locks 13 of the leftmonomer 1 in order to free the right monomer 1 for movement.

[0099]FIG. 15g shows the other case of a complementary lock. To free theright monomer 1 for movement in the desired direction, the complementarylock is first converted to a face lock, in which the right hand monomer1 has all four of its locks 13 extended, by the left monomer 1withdrawing its extended pair of locks 13, lying along the direction ofthe intended movement, and the right monomer 1 extending itscorresponding pair. The right monomer 1 then withdraws the other of itspairs of locks 13, leaving engaged the pair of locks 13 along the axisof which it is desired to move the right monomer.

[0100] Monomers 1 once freed to move are moved by selectively activatingthe motors 24 on the fixed structural monomers 1. The power to thesemotors 24 need not all be switched on at the same time on a long trackof adjacent monomers 1. The power can be switched on to the monomers 1that are to transport another monomer 1 shortly before the movingmonomer is due to arrive. Some time is allowed for each monomer 1 tospeed up and slow down its traction motor 24.

[0101] While movement is affected through the use of gears 23 and theextensible locks 13 with toothed wedges 14, there is a mechanicalproblem in making sure that monomers 1 arrive at their destinations andstop accurately with all four locks 13 of a face properly aligned, arequirement if power and data connections are to be made and ifstructures are to be built with accuracy. These problems are caused byinertia of the moved monomer 1, inertia of the motor 24 and gearmechanisms, and by tolerances in the machining of the parts. A largepart of the inertia problem can be solved by slowing down the monomers 1as they approach their desired positions, but the remaining problem ofmachining tolerances is such that with this design of the monomers 1,some further means for ensuring accurate positioning of the monomers atthe end of a movement may be required.

[0102]FIGS. 16a and 16 b show one form of mechanical stopper mechanism,for one face of the cubic monomer 1, for locating a moving monomer 1 inposition. The stopper mechanism comprises four spring studs 28 locatedin the major grooves 11, one near each edge of the face of the cube.Each of the four studs 28 is spring mounted on a common carrier 29. Thecarrier 29 is used to extend the studs 28 into the major groove 11 foruse, and to retract them when they are not required. The carrier 29 isactuated by a solenoid or linear motor 30. The outward facing edges ofthe studs 28, those edges nearest the edges of the face of the cube, arechamfered. That and their spring mounting on the carrier 29 allows themto be depressed back into the body of the monomer 1 by the locks 13 ofan advancing monomer. The inward facing edges are not chamfered and sothe studs 28 act as a trap. The locks 13, which are the part of theadvancing monomer 1 that contact the studs 28, should also have lightlychamfered edges to allow a smooth entry into the trap. As shown in FIG.16, the studs 28 are biased into the extended position by a compressionspring 32. This action can be assisted by reversing the action of thesolenoid 30.

[0103] The design of the spring stud mechanism is such that the trap canbe activated even after a travelling monomer 1 has partially entered thetrap, which is desirable for a number of applications.

[0104] The trap works only in one axial direction at any one timebecause an advancing monomer 1 has only one pair of its locks 13extended; nothing comes into contact with the studs of the other axis.Therefore all four sprung studs 28 can be connected to the same carrier29 and solenoid 30.

[0105] Once the moving monomer is in position, the forces on the sprungstud mechanism are preferably minimised by immediately locking the twomonomers together with either a complementary lock or face lock.Otherwise the sprung studs could become distorted and jam in theirsockets.

[0106] The default action of the spring 32 on carrier 29 is to extendthe studs 28. This action is desirable for stopping moving monomers 1should sudden power failure occurs.

[0107] Referring now to FIGS. 17 and 18, a second form of cubic monomer33 has on each face four symmetrically positioned grooves, each runningparallel and fairly close to a respective edge of the face. Each groovecomprises a slot 34 at 45° to the face of the cube, angled towards thecentre of the cube, and a similar slot 41 angled away from the centre ofthe cube.

[0108] Like the first form of monomer described above, the second formof monomer uses two pairs of locks for each face of the cube 33. Eachlock comprises a wedge 35 that can be extended out of and retracted intoone of the slots 34 and, when extended, engages in the slot 41 of anadjacent monomer. The slots 34 and 41 are so positioned that they arealigned when two monomers are face-to-face with the correct spacingbetween them. Each pair of locks comprises the locks near opposite edgesof a face of the monomer 33. The wedges 35 of each pair are linked byflexible rods 36 to a common linear actuator mechanism 37. As shown inFIG. 17, the linear actuator 37 comprises a motor 21, a screw shaft 22,and a ball-and-socket decoupling mechanism 40 similar to those shown inFIG. 6.

[0109] On locking, the flexible rods 36 are tightly sprung, and do notallow the wedges 35 to be pushed back into the slots 34. The ends of thewedges 35 have toothed racks 42. When inserted into another monomer 33,the teeth 42 on each wedge 35 engage a pinion gear 43 of the othermonomer 33. Driving the gears 43 slides the monomer 33 with the extendedwedges 35 along. An enlarged detail of the gear 43 and the toothed edgeof the wedge 35 is shown in FIG. 17b.

[0110]FIG. 17b, being a cross section, shows only one pair of wedges 35of each monomer 33. As mentioned above there are two such pairs to anyface. A diagrammatic representation of all four wedges 35 of a face, inthe extended position, is shown in FIG. 17c.

[0111] As shown in FIG. 17b, the axes of the gears 43 are parallel tothe associated face of the monomer 33, and the gears can be arranged inpairs on a common shaft, engaging the two wedges 35 of a pair. Each pairof slots 41 will be provided with a plurality of such pairs of gears 43,which are preferably driven from a common motor by a system of gearswheels and/or drive belts. If a corresponding change to the teeth 42 ofthe wedges 35 is made, the axis of the gears 43 can be turned 90° asshown in FIG. 17d. All of the gears 43 for a face of a monomer 33 thenhave parallel axes and can be driven from a single motor by a commontoothed belt.

[0112] The traction mechanism of the second form of monomer 33 istherefore similar to that of the first form of monomer 1, and themethods explained above, with reference to FIGS. 14 and 15, forconverting between the face lock, the complementary lock and slidingconfigurations are the same as for the monomers 1. The monomers 33 alsoemploy a stopper mechanism. The monomers 33 have similar electricalmeans 15 mounted on the wedges 35 or on the face of monomer 33 inmethods similar to monomer 1 to pass power and data and preserve thefour fold rotational symmetry of the face.

[0113]FIGS. 18a and 18 b both show two engaged monomers 33. FIG. 18ashows a single pair of wedges 35 extended from the left monomer 33 intothe right in a sliding configuration. Activating the gears 43 of theappropriate face of the right monomer 33 would move the left monomer 33into or out of the plane of the paper. FIG. 18b shows the pairs ofwedges 35 of the left monomer 33 extended into the right monomer 33 in aface lock.

[0114] An advantage of the monomers 33 over the monomers 1 is that theyrequire no equivalent to the wedges 14 of the locks 13 of the monomers1. Once a pair of wedges 35 of one monomer 33 is inserted into anothermonomer 33, the 90° angle between the wedges 35 automatically ensuresthat the monomers 33 cannot be separated. There is no need for anyfurther member to be extended from the wedges 35.

[0115] The monomers 33 have a number of other advantages over themonomers 1. They are simpler to implement. Their wedge locking mechanismoccupies less depth in its monomer. Their wedges 35 are much thinnerthan the locks 13 of the monomers 1, saving material and machiningcosts. Their wedges 35 are lighter in weight and travel through ashorter distance, resulting in a quicker locking mechanism. The monomers33 are cheaper than the monomers 1 to machine and construct. The singlegroove mechanism is mechanically less sound in design with features thatlead to greater stress concentration and consequent breakage and/or leadto a mechanism that is more prone to mechanical jamming than the doubleslot mechanism. One such feature is that the locks 13 are narrow whencompared to the distance between a pair of wedges 35 which is almost thefull width of a monomer 33.

[0116] Referring to FIGS. 19 to 22, the third form of monomer 44, likethe first form, has a single major groove 47 in each direction acrosseach face. The monomer 44, however, has a hinged lock mechanism, whichin some respects is simpler to construct and implement than either ofthe locks described above. FIG. 19 shows a partly complete monomer 44employing the hinged lock mechanism. The monomer has a cubic base unit45 with a face unit 46 mounted on each of the six faces of the baseunit. The grooves 47 are formed in the outer faces 54 of the face units46. Each groove 47 is T-shaped in cross section. FIG. 20 shows how twoopposing face units 46 of different monomers 44 lock together. At thebottom of each of the four arms of the cross shape formed by the grooves47 there is provided a pair of locks 48 which are hinged to pivot aboutaxes parallel to the length of the groove 47. These locks can pivotbetween two positions. In the disengaged position they lie flat alongthe bottom of the groove 47. To reach the engaged position they arepivoted through 90°. In that position they extend into the groove 47 ofan opposing face unit 46. Each lock 48 is provided with two grooves 49and 51, extending parallel to the length of the groove 47. The firstgroove 49, further from the pivot axis, engages one of the two lips 50provided by T-shape of the groove of an opposing face unit 46. The locks48 of a pair engage respective ones of the two lips 50. The secondgroove 51 receives the corresponding lip 50 of each lock's own faceunit, allowing the lock to reach its engaged position.

[0117] To facilitate relative motion of two monomers 44, each lock 48 isprovided at its extremity with a rack 52 for engaging pinion gears 53mounted in the groove 47 of an opposing face unit 46. The gears 53 aremounted to rotate about axes normal to the outer face 54 of the faceunit 46.

[0118] The considerations of which locks to engage and disengage aresimilar to those for the monomers 1 and 33 except that the locks are notmoved in pairs but fours consisting of all the locks located within thetwo opposite arms of one of the grooves 47 of a face unit 46, that isall the locks 48 along one of the two axes of movement of the monomers33.

[0119]FIGS. 21 and 22 are cross sections, like FIG. 20, of a face unitof a monomer 44, which show only half of a face unit.

[0120]FIG. 21 shows an alternative design of the hinged lock mechanismwhich differs from FIG. 20 in that each of the locks 48 has at itsextremity a transverse projection 60 instead of the groove 49. Thisprojection locks a monomer to its neighbour by engaging a slot 61 in thewall of the groove 47 of the neighbour.

[0121]FIG. 22 includes additional construction lines 62 and 65 to showthe clearance space 64 that is needed to allow the lock to swing intothe groove 49. This clearance space can be minimised (for example bymaking the transverse projection 60 and the slot 61 follow the arc ofthe curve 65) to avoid mechanical vibrations. Similar to rack 52 in FIG.20, there is a rack 52 on the tip of the transverse projection 60. Therack 52 engages pinion gear 63 (not shown in FIG. 22) as before.

[0122] Instead of a mechanical mechanism for interlocking monomers toeffect the relative motion of and securing of monomers, three differentdesigns of which have been discussed above, it is possible to providemonomers that have smooth faces and are moved and secured relative toeach other by means of electromagnets buried within the monomers.

[0123] Transport of monomers is provided by linear motors, whichcomprise electromagnets. The linear motors of stationary monomerslevitate the monomers that are to be transported. With carefulco-ordination of the linear motors of a row of stationary monomers, ahigh speed of transport along the row could be achieved.

[0124] Linear motors of conventional design would not allow monomers tobe transported vertically up the sides of stationary monomers nor alongtheir undersides, but that could be effected by provision of attractiveas well as repulsive windings in the linear motors.

[0125] Magnetically interacting monomers, unlike the monomers withmechanical locks, would not be limited to motion in directions alongrows of monomers. With suitable phasing of the excitation of theelectromagnets a monomer could be made to travel diagonally across asheet of monomers.

[0126] Accuracy of motion could in principle be achieved by carefulco-ordination of the windings of the monomers. Feedback for control ofthe motion of monomers, to see, for example, when a monomer has reachedits destination, is provided by optical sensors mounted in theirsurfaces. Preferably, velocity as well as position sensors are provided.Ideally the windings would be arranged so as to tend to move themonomers back towards its ideal position or path automatically, withoutthe need for feedback, when it departs from that position or path.

[0127] When monomers first arrive in position they can be held in placeby electromagnets. That method would however, limit the strength of anystructure formed from the monomers and would be wasteful of the powerrequired for the electromagnets. Mechanical locks could be provided totake over from the electromagnets or braces 55 as shown in FIG. 23 couldbe employed. The braces 55 are transported by means of the linear motorsand are engaged mechanically onto the electromagnetic monomers 56.

[0128]FIG. 23 also illustrates a method of strengthening a wall 57 builtfrom the monomers 56. The wall 57 has the horizontal rows of eachvertical plane of monomers making up the wall staggered for the samereasons that ordinary bricks are. The parallel can be continued byproviding special shaped monomers, such as ones of half length and/orones of one and a half length to fill gaps.

[0129] Electrical connection for power and data between the monomers 56is provided by a number of contacts on the surface of the monomers. Thecontacts are selectively utilised depending on their registration withthe contacts of a neighbouring monomer.

[0130] These electromagnetic monomers 56 can be used to buildfrictionless machines in which parts composed of the monomers are movedwithout touching relative to each other under the influence of theelectromagnets. The power required is likely to be high.

[0131] The weight of the electromagnetic monomers is of importance intheir design. Much of the weight of electromagnets is in their cores.Therefore recent advances leading to the development of coreless steppermotors, which are very much like linear motors, will be applicable tothe electromagnetic monomers.

[0132] In order to form machines and structures from monomers, it isnecessary for the monomers to transport each other around in aco-ordinated manner so that monomers end up in their desired position.That requires the transmission of data between monomers. It is alsodesirable that power, usually electrical power, is distributed to amonomer, from some central source, via its neighbours. That avoids thedisadvantages of weight, finite length of operation, and cost thatbatteries would have. Below will be discussed connections betweenmonomers for transferring power and data between them and also means fordirecting data and power received by a monomer at one of its faces toone or more of its other faces. These will be generally applicable toall the types of monomer discussed above.

[0133]FIG. 24 shows a two dimensional representation of a cubic monomer70 as a hexagon where the sides 71 of the hexagon correspond to thefaces of the monomer. Shown in the Figure is one form of the connectionsbetween the faces in the case where the monomers are under the controlof a single external computer. Each face is connected to a power bus 72,a routing bus 73, a data bus 74 and a synchronisation bus 75 viaswitches 76 which may be relays or semiconductor devices. Some of thesebusses comprise more than one conductor in parallel. The switches forconnecting a particular bus to a particular face can be can be operatedindependently. Signals and power carried on the busses are transmittedbetween the faces of neighbouring monomers via contacts on their locks,or in the case of the electromagnetic monomers 56 via contacts on theirsurface. The switches are provided to enable contact between twomonomers to be broken even when contact between neighbouring faces ismade.

[0134] The power bus 72 is provided to distribute power to the monomersfrom some external source. In general it is not necessary for theconnection of the power bus 72 between neighbouring monomers to bebroken by use of the switches except, to prevent arcing, when thephysical connection is about to be broken by withdrawing a lock. In theelectromagnetic monomers it is convenient for the power bus 72 tocomprise several lines each carrying a different phase of alternatingcurrent for the various electromagnets making up the linear motors.

[0135] The routing 73, data 74, and synchronisation 75 busses arepreferably buffered for some purposes and switches are provided toconnect, when desired, the necessary amplifiers into the lines of thebusses. Either the lines of the busses are bi-directional or there areprovided input and an output version of each line at each face.

[0136] If lines are bi-directional then the common bus scheme of FIG. 24has to be modified. For each line, switches are provided to divide eachline into segments and an amplifier is provided. The switches areoperated to connect the desired input face to the input of the amplifierand to connect the output of the amplifier to the desired output faces.

[0137] If separate input and output lines are provided then there is noneed to divide the lines. Buffering is provided for each input andoutput line pair simply by connecting an amplifier between the inputline and the output line.

[0138] The routing 73 and data 74 busses have related functions. Therouting bus 73 carries signals instructing the monomers to operatedtheir switches so as to connect particular monomers to the externalcomputer via the data bus 74. It is usual for all stationary monomers tobe connected to the external computer via the routing bus so that thedesired data bus connections can be established quickly. In the casewhere some or all the monomers have controlling computers, the routingbus is used to establish connections between monomers. The routing busalso carries information relating to which monomer or monomers shouldtransmit and receive over the data bus.

[0139] The data transfer over the data bus 74 includes, for example,instructions for monomers to operate their locks and traction motors,messages that monomers have reached their desired positions, andmessages that a monomer has become faulty. To ensure compatibilitybetween monomers made by different manufacturers, it is desirable forall monomers to obey the same protocol for reading and writing to therouting bus 73. A greater degree of flexibility is possible with thedata bus 74 and this is desirable in that specialised monomers orordinary monomers performing different functions may need to senddifferent sorts of data and to send data at different speeds. Therouting bus 73 is therefore also used to transfer signals to themonomers instructing them as to which protocol to use for the data bus74. Any given monomer need only be provided with hardware for readingand writing to the data bus according to the protocols useful to it.

[0140] The synchronisation bus 75 is used to ensure that monomers carryout physical actions in a synchronised manner. For example, a group ofmonomers may be instructed to perform an action, for example, to starttheir motors to move a group of monomer that are locked together. Theythen all start their motors together on receipt of a signal on thesynchronisation bus 75. The routing bus 74 is used to send signals thatdetermine which monomers receive a particular signal on thesynchronisation bus. The routing bus is also used to send information tomonomers as to which monomers should react to the synchronisation signalon the synchronisation bus.

[0141] The configuration bus architecture described here is preferred topacket switching for transferring data between monomers because withpacket switching it is not certain when data will arrive at itsdestination, making it difficult to know when to issue synchronisationsignals, and also because packet switching would require the provisionin the monomers of much logic to control the transfer of packets and tostore them for forwarding.

[0142] The contacts on the locks of the monomers, or on the surfaces ofthe electromagnetic monomers, are so arranged that when a monomer islocked in position each contact is in contact with a correspondingcontact of its neighbouring monomer. For cubic monomers, where many ofthe lines of the busses are in input and output pairs there is aparticularly convenient arrangement for the contacts. For each face ofthe cubic monomer, four contacts for each line are placed in positionspreserving the four-fold rotational symmetry perpendicular to the face.Unpaired contacts are placed either on the diagonal or on the orthogonalcentre lines of the face. For the paired contacts, the contacts of apair are placed symmetrically to either side of the orthogonal lines orto either side of the diagonal lines. In this arrangement, each unpairedline of a monomer is brought into contact with the same line of aneighbouring monomer and each input line of a monomer is brought intocontact with the corresponding output line of its neighbour and viceversa. Thus the monomers can be added to the material in anyorientation, obviating the need to know which way up and round anymonomer is. Such as arrangement for the monomers 1 is shown in FIG. 25which shows one face of the monomer in plan. The contacts, as mentionedearlier, are positioned on the locks 13. On the centre lines 80 areplaced the power contacts 81 and the synchronisation contact 82, and toeither side of these are the data bus in 83 and out 84 contacts and therouting bus in 85 and out 86 contacts.

[0143] As mentioned earlier, to build structures from and to operatemachines built from monomers they have to be supplied with controlsignals. While in principle an operator with a suitable generator couldissue instructions one at a time for particular monomers to operatetheir locks and to be moved one monomer along, up or down, this is anextremely tedious way to proceed. With a suitably programmed computer,the operator would ideally need only to specify the configuration of astructure or the various configurations of a machine and the computerwould work out all the movements of monomers necessary and would issueall the required instructions to the monomers to operate their movementmotors and their locks.

[0144] A more achievable solution between those two is for the operatorto analyse the construction of a structure into some fairly generaloperations; a suitably programmed computer is then used to convert theseoperations into the individual instructions to the monomers. Someexamples of general operations are discussed below.

[0145] The normal and L-type streamers shown in FIG. 3 are examples ofgeneral operations and they will now be discussed in detail. FIGS. 26a-eshow stages in the growth of an L-type streamer 8. FIG. 26a shows thestreamer after some growth has taken place. Five monomers 101, 102, 103,104 and 105 are arranged in a row with 105 being the tip of the streamer8. A monomer 106 is above monomer 104. FIG. 24b shows another monomer107 advancing along the top of monomers 101, 102, 103. On reachingmonomer 103, monomer 107 engages monomer 106 (see FIG. 26c). Monomers107 and 106 are then advanced as a pair until monomer 107 is abovemonomer 105, in which position (see FIG. 26d) monomer 106 projectsbeyond the tip of the streamer 8, monomer 105. Monomer 106 is thenlowered from monomer 107 to the position in front of monomer 105 tobecome the new tip of the streamer 8 (see FIG. 26e). The configurationof the monomers is now similar to that of FIG. 26a except that thestreamer is now one monomer longer. For the streamer to grow further,the cycle of operations shown in FIGS. 26a-e is repeated. It is a simplematter to program a computer to issue instructions to the monomers so asto grow a streamer. All the operator needs to do is to specify how longit should be. While the direction of growth of the streamer shown inFIGS. 26a-e is to the right, similar methods could be used to extendstreamers in any of the orthogonal directions.

[0146]FIGS. 27a-e show stages in the growth of a streamer 8 which issimilar to that of FIGS. 26a-e except that each monomer in FIGS. 26a-eis replaced by a block of 2×2×2 monomers. These blocks are moved in thesame way as are the single monomers of FIGS. 26a-e.

[0147]FIGS. 28a-d show stages in the growth of a streamer 8 in whichsome of the units corresponding to the single monomers of FIGS. 26a-eare 2×2×2 blocks of monomers and some are large monomers 110 equal insize to the 2×2×2 blocks.

[0148] These large monomers 110 are not simply the standard monomersscaled up but have the same sized locks repeated at positions over theirfaces appropriate for interacting with the standard monomers. The largemonomers 110 may additionally employ larger scaled up locks 13 forinteracting with similar monomers 110. The larger locks 13 are forgreater strength and to allow higher power motors 24 to move monomers110 at higher speeds.

[0149] In the examples of streamers described above, the streamers havebeen narrow, which is not always the case. Wall and sheets of monomerscan be grown using a streamer method using a unit which is many monomersin breadth. Alternatively, walls and sheets can be made by growingindependently a number of adjacent parallel streamers.

[0150]FIGS. 29a-f shows a method by which a streamer can be made to turna corner. In FIG. 29a there is a monomer 116 on top of the tip monomer115 of a streamer 111, 112, 113, 114, 115. A new tip to the left ofmonomer 115 can be provided by advancing a monomer 117 along the leftside of the streamer as is shown in FIGS. 29b and c. If however, it iswished to have the new tip on the right side of the streamer but it isdifficult to advance a monomer up that side, the configuration of FIG.29c can be manipulated to provide a new tip on the right side (see FIGS.29c-f). Firstly the monomer 107 is moved up from monomer 115 to monomer116. Next monomers 116 and 117 are moved as a pair so that monomer 117moves to the position above monomer 115. Then monomer 116 is moved downfrom monomer 117 to become the new tip to the right of monomer 115.Monomers to extend the streamer further can then be advanced along thetop of the streamer, pausing at monomer 115 to change direction by 90°.

[0151] The methods of turning a corner shown in FIGS. 29a-f can beapplied to 2×2×2 blocks of monomers. An alternative method is shown inFIGS. 30a-i. Firstly a 2×2×2 block is advanced to the position above thetip. Next that 2×2×2 block is moved one monomer, half its width, acrossto one side (FIG. 30a) and then the four monomers projecting over theside of the streamer tip are moved together down one monomer (FIG. 30b).The uppermost two monomers are moved together across to be on top ofthose four monomers (FIG. 30c). The resulting wall of six monomers ismoved down one monomer (FIG. 30d). The uppermost monomers are now a 2×2sheet which is moved across one monomer so that two of those monomersproject (FIG. 30e). The projecting two monomers are then moved down onemonomer (FIG. 30f) and the other two monomers of what was the 2×2 sheetare moved across one monomer to be on top of them (FIG. 30g). Finallythose four monomers, now a 2×2 wall, are moved down one monomer (FIG.30h). The resulting configuration has a 2×2×2 block of monomers to oneside of the old tip of the streamer (FIG. 30i).

[0152] The growth of the normal streamer was explained earlier and itwill be clear that, like the L-type streamer, the process can be appliedto blocks of monomers and mixtures of monomers of different sizes.

[0153] The streamer methods are reversible in that reversing their stepsresults in the streamers being retracted.

[0154] Both of the methods above-described of extending streamersrequire a supply of single monomers or other units at the base of thestreamer. Clearly the units need to be supplied from somewhere. Acollection of monomers that are free to be supplied and are groupedtogether in one place will be called a reservoir. A reservoir method isone for supplying monomers from a reservoir to a particular position onits boundary which will be called its gateway. That term can also beapplied to the position to which monomers must be supplied for thegrowth of a streamer.

[0155] Generally the gateway of a reservoir will be distant from thegateway of a streamer. The gateways can be linked by collections ofmonomers which will be called highways because usually they have theform of a narrow strip of units. Highways can easily be constructed byusing streamers. Once a highway has been built, units can be transportedalong the highway from one gateway to another.

[0156] A method of constructing a structure from a programmablematerial, starting with a reservoir of units is as follows: first ahighway is built from the gateway of the reservoir to the gateway of theproposed site for the structure, then monomers are delivered from thereservoir to the site, where they are used to construct the structure.The exact method used to construct the structure will depend on its formbut most structures can be analysed into sheets, walls and elongatemembers all of which can be formed by using streamers. As theconstruction of a structure progresses the points at which monomers needto be delivered can be distant from the gateway to a site. In suchcases, part of the structure can be designated as highways fortransporting monomers from the site gateway to where they are needed.

[0157] Some further consideration to be taken into account are thatthroughout construction, the structure has to remain mechanically stableand that it may not always be possible to supply the monomers fastenough during some periods. A solution to that problem is to providereservoirs inside the construction site, which can take up monomersduring times when demand is not so great.

[0158] Another method to consider using in the construction of astructure is to assemble part of it somewhere else before moving it toits final position. Consider for example the tower 120 of FIG. 31, whichcomprises two decks 121 supported by a pillar 122 at each corner. Thedecks are 4×4 squares, or cross shapes if the corner monomers arecounted as part of the pillars. This structure could be constructed byfirst raising the four pillars 122 and then bridging between them toform the two decks 121. Because the pillars are many monomers high andnot absolutely rigid, they will in practice not be an exact number ofmonomers apart at the top. That makes the bridging difficult to achievesince monomers attached to one pillar must engage precisely withmonomers of another pillar.

[0159] A better method is to first assemble on the ground a block ofmonomers 4×4 in plan and 2 monomers high to form the two decks stackedon top of each other and the bottom two monomers of each tower, and thento raise the four pillars at the corners of the block. Finally to finishthe tower 120 it is only necessary to raise the cross shaped decks tothe required heights. As the decks are raised they constrain the towersto being exactly two monomers apart.

[0160] When constructing large structures, it is useful to build thedeeper structural components first and then add the surface detailslater. The deeper structural components can be switched off once theyare in position leaving only the actively deforming skin layer poweredup saving considerable energy.

[0161] Some structures will require vast numbers of monomers. It is tobe expected that from time to time a monomer will fail. Such a monomercould be locked into the structure at some unimportant point. Ideally itshould, however, be removed from the structure and be deposited in aspecial reservoir or dump where it can cause no further problems.Monomers that are still functioning can be used to move faulty monomersand replace it with functioning monomers from another reservoir thusaccomplishing a self repairing task.

[0162] The self repair method can be extended to where many monomersfail simultaneously in a well defined cluster. Monomers unaffected bydamage but neighbouring the damaged cluster are used to move the damagedcluster as before and replace them with functioning monomers. Wheredamaged clusters may not need to be repaired and abandonment is moreimportant, damaged clusters are ejected by functional monomersneighbouring the damaged cluster by withdrawing their locks 13 from thedamaged cluster.

[0163] The method discussed above of analysing an amount of programmablematerial into objects such as streamers, highways, and reservoirs whichhave boundaries between them breached at a limited number of gateways,lends itself to the case where many or all of the control signals neededto operate the material are generated by computers inside some or all ofthe monomers. The computer or computers of each object need only concernthemselves with the functions of that object while from time to timeoverseeing the transfer of monomers via gateways to and fromneighbouring objects. For example a highway could be instructed to moveall monomers received at one gateway to another gateway, which task itcould proceed with without further external instruction.

[0164] The analysis of a machine made of monomers into parts comprisingseveral monomers is a useful first step in working out how to achievethe desired movements of the machine. The walker 6 of FIG. 2 is anexample of a simple machine. The parts it comprises are a body 130 whichis two monomers high, one wide and many in length, and six legs 131 eachthree monomers high. In their usual positions, the legs are joined attheir top monomer to the lower row of the body. The walker 6 can bemoved by moving the legs one at a time forward along the body and thensliding the body forward through the legs. The legs are moved by firstraising them up one monomer, then moving them along, and then movingthem down one monomer.

[0165] The monomers described above will not by themselves be able toprovide every type of machine. However, by providing specialised partsmounted on monomers, their utility can be greatly enhanced. As anexample of this, a lathe could be built from standard monomers alongwith a monomer with a cutting tool mounted on it and another monomerwith a rotatable chuck mounted on it. The standard monomers are used toprovide the frame of the lathe and a mechanism for advancing the cuttingtool into the workpiece.

[0166] There can be many specialised monomers that do particularspecialised tasks very well. A few described below greatly enhanceusefulness in general applications. One such monomer is an adjustablefoot unit. An adjustable tipped rod extended from a specialised monomeracts as a foot unit which can be used to level structures that areerected. The walking mechanism described earlier would benefit from sucha foot unit attached to legs 131 on an uneven surface.

[0167] Another specialised monomer is one with a wheel which may bepower assisted, steerable and have brakes. Several such wheeled unitscould support a structure which can then be made mobile on a reasonablyflat surface. Such a machine would be expected to travel faster than awalking machine.

[0168] Yet another specialised monomer is one which is substantially airtight and posses an air cavity so as to bear much more weight thatitself in a liquid medium. A collection of such monomers allows astructure to be supported above it in a liquid medium such as water oroil.

[0169] The three specialised monomers described above substantiallyincrease the multi-terrain capability of monomers. That is, monomers canthen negotiate rough ground, level ground and water which a typicalrequirement for a multi-terrain vehicle. Where rough ground includesobstacles, programmable materials simply deform around the objectthrough the use of streamers, highways, reservoirs and gateways.Computers with software for terrain negotiation and sensors for obstacledetection are needed to perfect such machines.

[0170] Another useful specialised monomer is one which allows rotation,free or powered, of opposite ones of its faces about the axis throughtheir centres. This allows machines in which parts built of monomersrotate relative to each other. Two such monomers can be used to supportlong objects, one monomer supporting each end, along tortuous highways.

[0171] Of the myriad possible uses of programmable materials two moreare mentioned by way of example. Because of their flexibility,programmable materials are useful in disaster situations with hostileenvironments. For example, in a damaged nuclear power stationprogrammable material could be used to erect, without the need forpeople to enter damaged area, strongly radiation-blocking walls to arequired shape and thickness. In such a situation the monomers would beparked to eliminate the gaps that they usually have between them.

[0172] Again because of their flexibility, programmable materials wouldalso be useful in military engineering, for example, in the constructionof temporary bridges. Such bridges could be programmed to be selfrepairing after being damaged.

1. A machine of substantially parallelepiped shape, having means for so interacting with identical machines as to cause relative transport of them and the machine, and means for interacting with identical machines so as to secure the machine in position relative to them.
 2. A machine according to claim 1 which is responsive to external signals communicated to it so as to effect the transporting and securing.
 3. A machine according to claim 1 or claim 2 incorporating a computer and which is responsive to signals generated by that computer so as to effect the transport and securing.
 4. A machine according to any one of claims 1 to 3 wherein the securing means or transporting means or both comprise electromagnets.
 5. A machine according to any one of claims 1 to 3 wherein the transporting means or securing means or both comprise mechanical parts or features on the machine that interlock with complementary parts or features on identical machines.
 6. A machine according to claim 5 wherein the transporting means comprises mechanical parts or features on the machine that can be caused to interlock with complementary parts or features on an identical machine in such a manner as to allow relative motion of the machines along particular axes.
 7. A machine according to claim 6 wherein the parts or features are arranged to provide two or more independently engageable interlocks between machine and an identical machine, each of which allows relative motion of the two machines only along a respective one of two or different axes.
 8. A machine according to any of claims 5 to 7 wherein the interlocking parts or features comprise a member extensible from the machine into a recess or groove in an identical machine and wherein the member incorporates extensible wedges for locking the member in the recess or groove.
 9. A machine according to any one of claims 5 to 7 wherein the interlocking parts or features comprise pairs of members, the members of a pair being extensible from a face of the machine, in different directions at an angle to the normal to that face, into respective ones of a pair of recesses or grooves in a face of an identical machine.
 10. A machine according to any one of claims 5 to 7 wherein the interlocking parts or features comprise pairs of members, each member of a pair being mounted to pivot between a withdrawn position and an extended position.
 11. A machine according to claim 10 wherein the members of a pair receive at their extended positions, in respective grooves in the members, respective ones of a pair of opposing lips of an identical machine.
 12. A machine according to any of claims 5 to 11 comprising a plurality of studs on a face of the machine engageable with a neighbouring identical machine so as to locate it in position, the studs being retractable so as to release the neighbouring machine.
 13. A machine according to claim 12 wherein the studs are engageable with the interlocking mechanical parts or features of the neighbouring machine.
 14. A machine according to claim 13 wherein the studs are depressible by an identical machine that is advancing to become such a neighbouring machine.
 15. A machine according to any preceding claim of substantially cuboid shape.
 16. A machine according to claim 15 of substantially cubic shape.
 17. A machine according to claim 15 having four means on each face of the machine for communicating power or data with neighbouring identical machines, those means being located in the same positions on each face and being so located either on each of the diagonal centre lines or on each of the orthogonal centre lines of each face as to preserve the four-fold rotational symmetry of the face.
 18. A machine according to claim 15 or claim 16 having four pairs of an input means and an output means for communicating data with neighbouring identical machines those means being located in the same positions on each face and the input means and output means of each pair being so located symmetrically to either side of each of either the diagonal centre lines or the orthogonal centre lines of the face so as to preserve the four-fold rotational symmetry of the face.
 19. A machine equivalent in size to a parallelepiped block of a plurality of machines according to any one of claims 1 to 18, that is not composed of such machines and that has means for so interacting with such machines as to cause relative transport and securing that would occur if the machine consisted of a parallelepiped block of machines.
 20. A structure or a machine assembled from machines according to any one of claims 1 to 18 or from a mixture of such machines and compatible machines according to claims
 19. 21. A method of moving by said means a first machine aligned with a first site, to a second site which is aligned with and neighbouring the first site, in a direction parallel to the neighbouring sites, wherein each site is a machine and wherein each of the machines is a machine according to claims 1 to
 19. 22. A method according to claim 21 wherein the first and second sites co-operate to move the first machine.
 23. A method of movement according to claims 21 and 22 which relies for stopping movement substantially on method in claim
 14. 24. A method according to claim 21, or claim 22, or claim 23, wherein the first machine has neighbours that are secured to it and that move with it.
 25. A method of moving a machine along a row of machines comprising repeatedly applying a method according to any one of claims 21 to
 24. 26. A method according to claims 21, 22, 24 and 25 wherein the motion of the machine along the row is continuous.
 27. A method of extending by one unit, a streamer of units in a row ending in a tip unit, the units either being single machines according to any one of claims 1 to 18, or being parallelepiped blocks of such machines or machines according to claim 19 or a mixture of the two, the method comprising moving a pair of units along the streamer until one of the pair is a neighbour of the tip unit and the other extends beyond the tip unit, and moving the other unit of the pair from being a neighbour of the one unit to being the neighbour of the tip unit, in which position it becomes the new tip unit, the movement of the machines being according to claim 21 and
 22. 28. A method of extending by one unit a streamer of units in a row beginning in a base unit, the units either being single machines according to any one of claims 1 to 18, or being parallelepiped blocks of such machines or machines according to claim 19 or a mixture of the two, the base unit having one or more neighbouring machines that are not in the row, the method comprising adding an extra unit to the row before the base unit and advancing the row relative to the one or more machines neighbouring the base unit a distance of one unit in the direction that results the extra unit moving to the original site of the base unit.
 29. A method of retracting a streamer comprising reversing the steps of either a method according to claim 27 or of a method according to claim
 28. 30. A method of delivering machines according to any one of claims 1 to 18, or to claim 19 or a mixture of the two, from a first point to a second point, comprising constructing from such machines a structure connecting the two points and moving the machines along the structure from the first point to the second point.
 31. A method of constructing a structure comprising machines according to any one of claims 1 to 18, or to claim 19, or a mixture of the two, the method comprising extending a streamer according to claim 27 or
 28. 32. A machine substantially as herein described with reference to, and as shown in, FIGS. 4 to 13, or FIG. 17, or FIGS. 19 and 20, or FIG.
 23. 33. A machine substantially as herein described with reference to, and as shown in, FIGS. 4 to 13, or FIG. 17, or FIGS. 19 and 20, modified as described with reference to, and as shown in FIG.
 16. 34. A method of moving machines relative to each other substantially as herein described with reference to, and as shown in, any one of FIGS. 26 to
 30. 35. A method of securing machines substantially as herein described with reference to, and as shown in, FIG. 14b or FIG. 14c.
 36. A method of moving machines substantially as herein described with reference to, and as shown in, any one of FIGS. 15d to g. 